I'm new to the fixie and I'm 230lbs. I also squat nearly 500lbs and a front brake is enough for me on my fixie(I have a surly flip flop). But I'm also running a high gear 48t chainring and a 15t cog(17 on the other side but I don't really use it), I just deal with hills on the up and its good down hill with the front brake.